1. Field of the Invention
This invention relates to an exhaust gas measuring device that measures exhaust gas discharged from an internal combustion engine of a vehicle and a method for measuring exhaust gas, and more specifically, to an exhaust gas measuring device and a method for measuring exhaust gas that makes it possible to obtain a workload of the internal combustion engine and an amount of exhaust gas per the workload.
2. Background Art
An exhaust gas measuring device that measures the concentration of a predetermined component such as CO, CO2 or NOx contained in the exhaust gas discharged from an internal combustion engine (an engine) provided for a vehicle and that analyzes the exhaust gas is known. (For example, Japan Patent Laid-open No. 8-128948.)
A main object of the exhaust gas measuring device is not only to know the concentration of a predetermined component contained in the exhaust gas but also to know the emission mass of the exhaust gas or mass of the predetermined component contained in the exhaust gas in order to measure what influence is exerted on atmospheric contamination by the exhaust gas discharged from the internal combustion engine.
An index calculated by converting the mass of the exhaust gas discharged from the internal combustion engine or the mass of the predetermined component contained in the exhaust gas into an amount per unit workload (unit output) of the internal combustion engine, namely the mass of the exhaust gas discharged from the internal combustion engine per unit output is used for performance assessment or legal restrictions of the internal combustion engine.
The index is used in a case that measurement is conducted for a stand-alone internal combustion engine such as an internal combustion engine of an especially large-size vehicle that does not have a large-size chassis dynamo meter accepted by the large-size vehicle.
Since the workload (output) of the internal combustion engine is expressed by a product of torque and a rotation number, the torque and the rotation number of the internal combustion engine have to be obtained directly in order to calculate the workload. However, it is not easy to obtain either of the torque and the rotation number, and there has almost never been an exhaust gas measuring device that is provided with a sensor to obtain the torque especially.
Then in order to obtain the workload of the internal combustion engine, conventionally there was a method to use torque data obtained by the use of an ECU by calculating the fuel injection amount injecting to a fuel engine or a method to detect torque by the use of a torque sensor actually mounted on a shaft of an internal combustion engine.
However, since the torque data obtained by the ECU is based on a fuel supplying amount near an internal combustion engine or an inhaled air amount, there exists a time-lag between the torque data and the data of the amount of the exhaust gas discharged from an exhaust duct (a tail pipe) arranged separated from the internal combustion engine. As a result, the contemporary discharged amount of the exhaust gas of the internal combustion engine per workload can not always be calculated. In addition, there is a problem that a torque sensor is extremely difficult to mount. Furthermore, there might be a case that a vehicle is not provided with an interface such as an ECU signal or an OBD to output the torque data to outside of the vehicle. In addition, even though the interface is provided, a signal mode may vary for each vehicle and is difficult to obtain. It is a situation that the workload of the internal combustion engine can not be measured accurately and easily.